SS2 Chemistry Lesson Note on Blocks of Elements

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BLOCKS OF ELEMENTS

From the position of the various elements on the periodic table and the electrons arrangements or configurations seem to stand out. Elements that have one and two electron(s) in their last s- orbital i.e. group 1 and 2 elements are called s-block elements.  P-block elements have their last electron (s) in the p-orbital are called P block elements.

Elements that have their last electrons in the d orbital are called d blocks elements while f block elements have their last electrons in the f- orbital.

Moving across a particular period on the periodic table, two elements are present in the S block, six elements in the P block, ten elements in the d- block and fourteen elements in the f- block. This corresponds with the maximum number of electrons in the s, p, d, and f orbitals respectively. Also, S block elements are metals, P block elements are mostly non-metals d- block elements are transition metals while f-block elements are lanthanides (rare earth metals) and actinides (heavy rare earth metals).

There is therefore a diagonal division of the elements into metals and non-metals as shown below. Metals are found on the left side of the thick boundary line and the non-metals on the right with metalloids occurring along the boundary line.

 CHARACTERISTICS PROPERTIES OF TRANSITION ELEMENTS

1. Paramagnetism: Transition elements exhibit paramagnetism because of the presence of unpair electrons in the d-orbital. Paramagnetism is the ability of an element to align to the poles of a magnet.
2. Variable oxidation states: Transition elements exhibit variable oxidation states because they can lose electrons from both 4s and 3d orbitals for bond formation e.g we have Fe²⁺ and Fe³⁺
3. Complex ion formation: Transition elements form complex ions due to the presence of vacant or empty d- orbitals in their ions.
4. Catalytic ability: The catalytic ability of transition metals is due to the fact that they exist in different oxidations states, hence they are used as catalyst. The partially filled d-orbital allows the exchange of electrons to and from molecules which enable them to act as catalyst.

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